Feeding by the western flower thrips, Frankliniella
occidentalis, causes damage to the fruits of pepper, and the species is the
key vector of Tomato spotted wilt virus. Effective management integrates
conservation of populations of the natural predator, Orius insidiosus,
with the use of reduced-risk insecticides, namely spinosad. We conducted field
experiments in northern Florida in 2005 and 2006 and in central Florida in 2006
to evaluate the new reduced-risk insecticide spinetoram for control of thrips
and to determine the impact on natural populations of O. insidiosus.
Spinetoram at 61 g ai/ha was as effective as spinosad at
140 g ai/ha against the western flower thrips and the
other common thrips in Florida, Frankliniella tritici and
Frankliniella bispinosa. The mean numbers of the predator were very high in
all treatments in each experiment, and their numbers relative to the numbers of
thrips indicated that predation was sufficient to suppress thrips populations in
all treatments. Broad-spectrum insecticides when included in the experiments
provided little or no control; sometimes, they flared thrips numbers compared to
untreated pepper.

Introduction

Thrips (Thysanoptera) are tiny insects with fringed wings. There
are over 5000 described species with about 87 species of thrips that are pests
of commercial crops due to their feeding on leaves, fruits, and flowers causing
discoloration, deformity, and reduced marketability (8). Figure 1 shows flecking
damage to a pepper fruit caused by the feeding of the adults and larvae
of the western flower thrips, Frankliniella occidentalis. The western
flower thrips of worldwide distribution is considered the primary vector of
Tomato spotted wilt virus (14). Symptoms of the disease include retarded
growth, chlorosis, necrosis, and the characteristic ring spots on the leaves and
fruits. Peppers display a range of symptoms, and the ring spots are not always
present on the leaves (Fig. 2). Other vectors in the southeastern US include
F. bispinosa and F. fusca (1). Another common thrips species in
crops in the southeastern US is the non-vector species F. tritici (13).
Chellemi et al. (5) noted that populations of each of the above-mentioned
species peaked during the peak flowering of wild host plants in northern Florida
between March and June. Large populations of F. occidentalis, F.
tritici, and F. bispinosa migrate into the spring crop of flowering
peppers, causing reduced-marketability from thrips feeding damage and from their
vectoring of Tomato spotted wilt virus (6,11).

Growers in the southeastern US responded in the late 1980s
and early 1990s to the invasion of F. occidentalis by the application of
broad-spectrum, highly toxic insecticides. These insecticides were sprayed on a
frequent calendar schedule in unsuccessful attempts to control thrips.
Funderburk et al. (6) showed that applications of fenpropathrin and acephate
suppressed thrips populations initially, but their numbers increased rapidly a
few days after application in numbers that were eventually many-fold greater
than untreated pepper. Successful management approaches were achieved through
the conservation of natural enemy populations. Minute pirate bugs (Anthocoridae)
are effective biological agents against thrips in greenhouses (12). Under field
conditions it was thought that the characteristics of rapid colonization and
population growth of thrips surpassed the capacities of natural enemies to
control them (9). However, Funderburk et al. (6) and Reitz et al. (11) showed
that natural infestations of the native anthocorid species, Orius insidiosus
(Say), were effective in suppressing populations of thrips, even under these
conditions. Tavella et al. (12) reported that over 96% of the immature and adult
stages of F. occidentalis and Orius spp. were aggregated in the
flowers of greenhouse peppers. Hansen et al. (7) reported similar patterns of
aggregation of Frankliniella spp. and O. insidiosus in field
pepper.

In much of the southeastern US, F. occidentalis and
Tomato spotted wilt virus are the key pest problems in pepper and other
crops (3). An effective integrated pest management program that employs
reduced-risk insecticides, natural infestations of O. insidiosus, and
cultural control tactics including ultraviolet-reflective mulch are widely
implemented for pepper (11). Spinosad (Dow AgroSciences, Indianapolis, IN) is
the most effective insecticide able to suppress populations of F.
occidentalis, and it is a reduced-risk insecticide that does not suppress
populations of O. insidiosus at labeled rates (6,11). Spinosad also is
effective in suppressing populations of numerous other occasional pests of
pepper.

Spinetoram (Dow AgroSciences) is a new spinosyn insecticide
that, like spinosad, is derived from the fermentation of Sacchanopolyspora
spinosa. Spinetoram is a reduced-risk insecticide because of its low
toxicity to many beneficial insects and because of its low human and
environmental toxicity.

Our purpose was to evaluate the compatibility of spinetoram for
control of thrips with biological control in field pepper. We tested a range of
rates of spinetoram for suppression of F. occidentalis, F. bispinosa,
and F. tritici in field pepper against the standard rate of spinosad. The
effects of these rates on natural populations of O. insidiosus were
determined.

Evaluation of Spinetoram on Thrips and Thrips Predator Populations

Field experiments were conducted in 2005 and 2006 at the
University of Florida North Florida Research and Education Center in Quincy,
Gadsden Co. Another experiment was conducted in 2006 at the University of
Florida Plant Science Research and Education Unit in Citra, Marion Co.
Six-week-old transplants of ‘Camelot X3R’ (Quincy experiments) and ‘Aristotle’
(Citra experiment) sweet pepper were transplanted into raised plastic beds
spaced 90 cm apart. Each bed consisted of two linear rows with 30-cm spacing
between and within rows. Beds were fumigated with methyl bromide at 339 kg/ha
about one week prior to transplanting. Plants were irrigated based on the plant
needs through a trickle tube at the center of each bed. Experimental design was
a randomized complete block with four replicates in each experiment. Plot size
was one two-row bed by 9 m. Foliar-applied treatments of spinosad 2SC and
spinetoram 1SC were included in each experiment. Foliar-applied treatments of
esfenvalerate 0.66 (E. I. DuPont de Nemours and Co., Wilmington, DE), novaluron
0.83EC (Chemtura Corp., Middlebury, CT), and spiromesifen 2SC (Bayer CropScience
LP, Research Triangle Park, NC) were included in some experiments. Imidicloprid
(Bayer CropScience LP) was applied through the trickle tube at transplanting to
selected treatments in the Quincy experiment in 2006. Foliar-applied
insecticides were applied with a backpack sprayer that was powered by
pressurized carbon dioxide and that was equipped with 4 D7 nozzles per
double-row bed. The amount of spray was 316 liters/ha. Application dates
were 18 and 25 May in the 2005 Quincy experiment. Application dates were 5, 10,
and 19 May in the 2006 Quincy experiment and 3, 11, and 18 May in the 2006 Citra
experiment. Treatments were evaluated for effects on insect populations two and
six days following the foliar insecticide application dates unless prohibited by
rainfall. The densities of adult thrips of each species, total larval thrips,
and adult and nymphal O. insidiosus were estimated in each plot on each
evaluation date by collecting 10 flowers per plot and placing them in vials
containing 70% alcohol. Thrips and O. insidiosus were extracted from the
flowers and identified using 7 to 80× magnification. Tests of data revealed no
serious departures from normality, and data analyses are reported for
untransformed data. Significant treatment differences for adult thrips of each
species, for total larval thrips, and for total adult and nymphal Orius
insidiosus on each sample date were determined using analysis of variance
for a randomized complete block and subsequent Duncan’s Multiple Range Test (P < 0.05). Significant treatment differences for the number of thrips of all
species and stages and for the number of O. insidiosus for data pooled
over all sample dates were determined for each experiment using analysis of
variance for a randomized complete block and subsequent Duncan’s Multiple Range
Test (P < 0.05).

Efficacy of Insecticides Against F. occidentalis and F. tritici

Populations of F. occidentalis were common in the Quincy
experiments, but not in the Citra experiment. Unlike northern Florida,
populations of F. occidentalis typically are only a small proportion of
the total thrips population in central Florida (7). Numbers in
the 2005 experiment conducted in Quincy were greatest on the 24 May sample date,
and this is the only date in which there were significant treatment differences
(F = 5.0; df = 5, 15; P = 0.06). The standard rate of spinosad and
the highest rate of spinetoram provided significant control as compared to the
untreated pepper (Table 1). Populations of F. occidentalis were much
greater in the experiment conducted in Quincy in 2006, especially on the 6, 9,
10, and 13 May sample dates when there were significant treatment differences (F = 2.0, 3.5, 2.3, and 2.8, respectively; df = 8, 28; P < 0.08, 0.01,
0.05, and 0.05, respectively). Treatments that included novaluron and
spiromesifen had numerically, but not statistically, higher numbers of adults
than untreated pepper on each of these sample dates (Table 2). The treatment of
esfenvalerate had significantly more adults than untreated pepper on the 10 May
sample date. This result is consistent with previous reports of pyrethroid
insecticides such as esfenvalerate flaring populations of F. occidentalis
in pepper (6,7,10,11). Treatments that included spinosad or spinetoram
usually had numerically lower numbers of adult F. occidentalis than
untreated pepper but the only significant difference was the highest rate of
spinetoram compared to untreated pepper on 13 May (Table 2).

Table 1. The mean number of adult Frankliniella occidentalis
per ten flowers on four dates according to treatment in the field experiment
conducted in Quincy, FL in 2005.

Treatment and active ingredient per hectare

Mean Frankliniella occidentalis adults
per 10
flowers*

20 May

24 May

27 May

31 May

untreated

2.3a

3.3a

0.0a

0.0a

spinosad 140 g

0.3a

0.7b

0.3a

0.0a

spinetoram 18 g

0.0a

2.0ab

0.8a

0.0a

spinetoram 26 g

0.8a

2.3ab

0.5a

0.0a

spinetoram 44 g

1.0a

1.3ab

0.0a

0.0a

spinetoram 61 g

1.3a

0.0b

0.5a

0.5a

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Table 2. The mean number of adult Frankliniella occidentalis
per ten flowers on six dates according to treatment in the field experiment
conducted in Quincy, FL in 2006.

Treatment and active ingredient per hectare

Mean Frankliniella occidentalis adults
per 10
flowers*

6 May

9 May

10 May

13 May

20 May

23 May

untreated

12.0abc

29.8abcd

12.0b

17.4a

4.6a

1.6a

esfenvalerate 56 g

6.0c

24.0bcd

28.8a

9.8ab

3.0a

0.5a

spinosad 140 g

20.5ab

23.3bcd

15.0b

8.8ab

5.5a

1.3a

spinetoram 26 g

11.0abc

10.8d

12.8b

8.8ab

3.0a

1.5a

spinetoram 44 g

10.8abc

10.5d

18.0ab

8.5ab

4.5a

1.3a

spinetoram 61 g

8.8bc

15.2cd

11.8b

5.3b

3.5a

0.5a

novaluron 87 g

22.3a

32.8abc

13.3b

14.0ab

3.5a

2.5a

imidicloprid 285 g
& novaluron 87 g

17.3abc

45.8a

24.3ab

17.5a

4.3a

0.8a

imidicloprid 285 g &
spiromesifen 145 g

15.0abc

42.5ab

15.8b

17.3a

6.3a

1.8a

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

The adults of F. tritici were more common in both of the
Quincy experiments than the adults of F. occidentalis. This species was
rare in the samples in the Citra experiment in 2006. The mean numbers of adults
by treatment in the 2005 and 2006 Quincy experiments are shown in Tables 3 and
4, respectively. The adults of F. tritici are highly vagile, and their
ability to re-colonize treated crops frequently results in an apparent rather
than real lack of control by short-residual insecticides (10). This was reflected in the results in our experiments in that there were
significant treatment differences on only the 31 May sample date in 2005 (F = 4.3; df = 5, 14; P = 0.05) and on the 6 and 9 May sample dates in 2006
(F = 2.9 and 3.9, respectively; df = 8, 28; P < 0.01). On the 31
May sample date in 2005, each insecticide treatment of spinosad and spinetoram
resulted in significant suppression compared to the untreated control. In the
2006 experiment, the application of novaluron resulted in significantly
increased numbers compared to untreated pepper on 6 May and the treatment of
imidicloprid and novaluron resulted in significantly increased numbers compared
to untreated pepper on 9 May.

Table 3. The mean number of adult Frankliniella tritici
per ten flowers on four sample dates according to treatment in the field experiment
conducted in Quincy, FL 2005.

Treatment and
active ingredient
per hectare

Mean Frankliniella tritici per 10 flowers*

20 May

24 May

27 May

31 May

untreated

4.5a

26.7a

84.0a

72.8a

spinosad 140 g

4.0a

34.7a

94.5a

32.5b

spinetoram 18 g

3.0a

29.7a

68.8a

27.0b

spinetoram 26 g

1.3a

32.7a

51.8a

31.0b

spinetoram 44 g

2.5a

30.3a

52.3a

27.0b

spinetoram 61 g

4.0a

63.3a

37.8a

29.8b

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Table 4. The mean number of adult Frankliniella tritici
per ten flowers on six sample dates according to treatment in the field experiment
conducted in Quincy, FL in 2006.

Treatment and active ingredient per hectare

Mean Frankliniellatritici per 10 flowers*

6 May

9 May

10 May

13 May

20 May

23 May

untreated

9.4bcd

6.1bc

2.4a

9.9a

10.0a

9.0a

esfenvalerate 56 g

5.0d

4.0bc

7.3a

2.3a

8.3a

4.5a

spinosad 140 g

12.8bcd

5.3bc

3.5a

3.5a

12.3a

8.3a

spinetoram 26 g

17.3ab

2.0c

3.3a

3.8a

6.3a

7.5a

spinetoram 44 g

12.5bcd

2.0c

4.5a

3.3a

6.3a

9.5a

spinetoram 61 g

5.8cd

4.8bc

2.8a

1.8a

5.8a

5.8a

novaluron 87 g

23.8a

4.3bc

3.3a

6.5a

8.0a

13.3a

imidicloprid 285 g
& novaluron 87 g

16.5abc

10.3a

5.0a

8.8a

12.3a

10.5a

imidicloprid 285 g
& spiromesifen 145 g

11.8bcd

8.3ab

5.3a

8.0a

9.5a

13.0a

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Populations of larvae in both of the Quincy experiments were
F. occidentalis and F. tritici. The mean numbers of larvae by
treatment in the 2005 experiment are shown in Table 5. There were significant
treatment differences on 20, 27, and 31 May (F = 7.4, 3.0, and 6.5,
respectively; df = 5, 15; P < 0.001, 0.05, and 0.01, respectively). Each
of the treatments of spinetoram provided significant control compared to
untreated pepper on these sample dates with no significant differences between
the rates of spinetoram. The standard treatment of spinosad provided significant
control compared to untreated pepper on 20 and 31 May. There were no significant
treatment differences on 24 May despite a many-fold greater number of larvae
estimated in untreated pepper compared to insecticide-treated pepper. The lack
of significant difference was due to poor precision of the sample estimates
combined with the fewer error degrees of freedom resulting from the loss of some
of the samples before processing. The mean numbers of larvae by treatment in the
2006 experiment conducted at Quincy are shown in Table 6. There were significant
treatment differences on 6 and 9 May (F = 8.0 and 4.8, respectively; df = 8, 28; P < 0.001). There were significantly greater numbers of larvae in
the esfenvalerate treatment compared to untreated pepper on 6 May. There were
significantly greater numbers of larvae in the imidicloprid and spiromesifen
treatment compared to untreated pepper on 9 May. There were numerically, but not
statistically, fewer larvae in the spinosad treatment and each of the spinetoram
treatments compared to untreated pepper on both dates.

Table 5. The mean number of Frankliniella larvae per ten
flowers on four sample dates according to treatment in the field experiment
conducted in Quincy, FL in 2005.

Treatment and active ingredient per hectare

Mean Frankliniella larvae per 10 flowers*

20 May

24 May

27 May

31 May

untreated

8.8a

34.3a

10.8a

44.8a

spinosad 140 g

2.3b

2.7a

7.5ab

4.5b

spinetoram 18 g

2.0b

6.7a

3.5b

5.0b

spinetoram 26 g

1.5b

6.0a

3.0b

2.3b

spinetoram 44 g

2.0b

4.8a

1.3b

3.3b

spinetoram 61 g

1.8b

3.7a

1.5b

0.8b

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Table 6. The mean number of Frankliniella larvae per ten
flowers on six sample dates according to treatment in the field experiment
conducted in Quincy, FL in 2006.

Treatment and active ingredient per hectare

Mean Frankliniella larvae per 10 flowers*

6 May

9 May

10 May

13 May

20 May

23 May

untreated

4.8b

14.4bc

20.4a

7.8a

4.5a

2.9a

esfenvalerate 56 g

16.5a

18.0ab

22.3a

12.8a

3.5a

1.8a

spinosad 140 g

1.5b

13.5bc

12.5a

9.0a

5.5a

2.8a

spinetoram 26 g

2.3b

4.8c

16.0a

7.0a

3.0a

2.5a

spinetoram 44 g

0.5b

4.8c

10.8a

8.0a

5.8a

2.5a

spinetoram 61 g

1.3b

3.5c

8.8a

3.5a

3.0a

2.8a

novaluron 87 g

2.3b

20.3ab

16.0a

8.8a

5.8a

3.8a

imidicloprid 285 g
& novaluron 87 g

4.5b

20.8ab

23.0a

12.3a

4.8a

2.8a

imidicloprid 285 g
& spiromesifen 145 g

4.3b

27.3a

23.8a

12.3a

4.8a

3.0a

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Efficacy of Insecticides Against F. bispinosa

The predominate species of flower thrips in pepper in central
Florida is F. bispinosa (7), and it was the predominate species in the
Citra experiment conducted in 2006. Populations of F. occidentalis and
F. fusca occurred in very low numbers. The thrips larvae were predominately
F. bispinosa. The mean numbers of the adults of F. bispinosa are
shown in Table 7. The adults of this species are highly vagile, and
re-colonization of insecticide-treated plots obviously affected the results.
There were significant treatment differences on 4 May when all of the
insecticide treatments resulted in suppression of adults compared to the
untreated control (F = 7.7; df = 5, 15; P < 0.001). The mean
numbers of larvae by insecticide treatment are shown in Table 8. There were
significant treatment differences on 4 and 23 May (F = 2.2 and 3.9; df = 5, 15; P < 0.10 and 0.01, respectively), with each insecticide treatment
resulting in significant suppression compared to the untreated control.

Table 7. The mean number of adult Frankliniella bispinosa
per ten flowers on six sample dates according to treatment in the field experiment
conducted in Citra, FL in 2006.

Treatment and active ingredient per hectare

Mean Frankliniellabispinosa per 10
flowers*

4 May

9 May

12 May

16 May

19 May

23 May

untreated

21.3a

21.0a

19.3a

6.6a

7.5a

40.3a

esfenvalerate 56 g

4.3b

11.8a

10.5a

7.3a

2.0a

13.5a

spinosad 140 g

7.0b

18.0a

11.8a

6.5a

2.8a

18.0a

spinetoram 26 g

4.5b

19.3a

18.3a

8.8a

3.3a

21.3a

spinetoram 44 g

4.3b

14.8a

12.8a

4.8a

2.5a

17.0a

spinetoram 61 g

4.0b

18.5a

8.3a

8.0a

3.3a

11.3a

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Table 8. The mean number of Frankliniella larvae per ten
flowers on six sample dates according to treatment in the field experiment
conducted in Citra, FL in 2006.

Treatment and active ingredient per hectare

Mean Frankliniella larvae per 10 flowers*

4 May

9 May

12 May

16 May

19 May

23 May

untreated

15.3a

3.5a

3.5a

1.3a

0.0a

3.3a

esfenvalerate 56 g

6.3b

1.0a

2.3a

3.8a

0.5a

1.0b

spinosad 140 g

6.5b

2.5a

0.3a

0.8a

0.0a

1.0b

spinetoram 26 g

6.8b

1.5a

1.5a

1.5a

0.3a

1.3b

spinetoram 44 g

8.0b

0.3a

0.0a

1.3a

0.3a

1.3b

spinetoram 61 g

6.0b

0.5a

0.8a

1.8a

0.5a

0.0b

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

Effects of Insecticides on Predator Populations

There were no significant treatment differences in the number of
O. insidiosus on any sample date in the 2005 and 2006 experiments in
Quincy. The mean number of Orius insidiosus per ten flowers for each
treatment for data averaged over all sample dates each year is shown in Table 9.
The mean numbers of the predator in relation to the mean numbers of total thrips
(i.e., combined numbers of adults and larvae of all species) were sufficient in
all treatments to suppress and usually to control populations of thrips. The
ratio of the mean number of thrips to the mean number of O. insidiosus
ranged between 18.1 and 75.0 for treatments in the 2005 experiment and between
9.8 and 24.0 for treatments in the 2006 Quincy experiment. Funderburk et al. (6)
showed that a ratio less than about 180 was sufficient for predation to result
in suppression of thrips while control of thrips occurred rapidly when ratios
were below about 50. Baez et al. (2) showed that O. insidiosus will prey
more heavily on the less mobile thrips larvae than on adults, but as abundance
of larvae declines predation on adults increases. This explains why the numbers
of thrips larvae (Tables 5 and 6) were much less on all sample dates in both
experiments than the number of thrips adults (Tables 1, 2, 3, and 4).
Consequently, predation prevented the buildup of thrips populations in the
peppers, even though there obviously was much immigration of adult thrips into
the pepper plots. Rapid movement of thrips from numerous plant sources to pepper
is typical in May in northern Florida (6,10,11).

Table 9. The mean number of Orius insidiosus and total
thrips of all species per ten flowers averaged over all sample dates according
to treatment in the field experiments conducted in 2005 and 2006 in Quincy,
FL and in 2006 in Citra, FL.

Treatment and active ingredient per hectare

Quincy, FL
2005

Quincy, FL
2006

Citra, FL
2006

Orius*

Thrips*

Orius*

Thrips*

Orius*

Thrips*

untreated

1.0a

75.0a

1.9a

30.0ab

9.4a

24.3a

esfenvalerate 56 g

—

—

1.9a

30.0ab

4.6b

11.0b

spinosad 140 g

1.0a

46.7ab

1.8a

27.6abc

4.3b

12.8b

spinetoram 18 g

0.5a

36.5b

—

—

—

—

spinetoram 26 g

1.1a

33.0b

1.4a

20.9bc

4.6b

14.9b

spinetoram 44 g

0.8a

31.4b

2.1a

20.6bc

4.5b

11.3b

spinetoram 61 g

1.9a

34.3b

0.8a

15.8c

4.0b

10.7b

novaluron 87 g

—

—

1.9a

34.2a

—

—

imidicloprid 285 g
& novaluron 87 g

—

—

1.8a

40.3a

—

—

imidicloprid 285 g &spiromesifin 145 g

—

—

1.6a

38.4a

—

—

* Means in the same column followed by the same letter are
not significantly different according to ANOVA and subsequent DMRT (P > 0.05).

There were significant treatment differences for O.
insidiosus on the 12, 19, and 23 May sample dates in the 2006 Citra
experiment (F = 11.3, 4.9, and 4.6, respectively; df = 5, 15; P < 0.001, 0.001, and 0.01, respectively). The numbers O. insidiosus in the
2006 Citra experiment were significantly less in each insecticide treatment
including esfenvalerate, spinosad, and each rate of spinetoram compared to
untreated pepper when the data was averaged over all sample dates (F = 5.4; df = 5, 15; P < 0.001) (Table 9). Spinosad was not reported in
previous publications to suppress O. insidiosus, although pyrethroid
insecticides including esfenvalerate were reported to suppress populations of
the predator (6,10,11). Ramachandran et al. (10) showed that the predator
moves rapidly between pepper plants in search of thrips prey. It is possible
that the predator was tracking populations of thrips; that is, they were moving
to and staying in greater numbers in the untreated plots with higher numbers of
thrips. The mean numbers of the predator in untreated pepper and in all
insecticide treatments were very high, and the number of thrips was very low
relative to the number of the predator (the ratio of the mean number of thrips
to the mean number of O. insidiosus ranged between 2.4 to 3.2 for all
treatments). These ratios indicated that predation had a great impact on
populations of thrips in untreated pepper and in all of the insecticide
treatments. Butler and O’Neil (4) showed that increasing thrips availability has
positive effects on the life history of O. insidiosus and that predation
rates of at least 20 thrips per day are necessary for optimal survival,
longevity, and egg production. Numbers of the predator were sufficient relative
to the number of thrips to prevent population buildup in all treatments (Table
9), and numbers of thrips larvae were less on all sample dates than the number
of adult F. bispinosa (Tables 7 and 8, respectively).

Spinetoram and Conservation Biological Control of Thrips

The combination of control of the invasive thrips species, F.
occidentalis, with spinosad and conservation of natural populations of O.
insidiosus is an effective integrated pest management program that is widely
adopted in the southern US (6,10,11). In these studies spinetoram at less than half the rate was
as effective as spinosad against F. occidentalis while conserving
populations of O. insidiosus. Lower rates of spinetoram provided
inconsistent efficacy against the adults and larvae. Spinetoram in these studies
was as efficacious as spinosad in controlling F. tritici and F.
bispinosa. Overall, spinetoram was as effective as spinosad in suppressing
the total number of thrips in the 2005 Quincy experiment, the 2006 Quincy
experiment, and the 2006 Citra experiment (F = 2.7, 5.0, and 5.2,
respectively; df = 5, 15; 8, 24; and 5, 15, respectively; P < 0.05,
0.001, and 0.001; respectively) (Table 9). Very few broad-spectrum insecticides
are available with efficacy against F. occidentalis, and populations in
pepper typically outstrip the toxic effects of broad-spectrum insecticides that
suppress populations of O. insidiosus (6,10,11). Flaring of the
populations of F. occidentalis by insecticides were rare in these
experiments (though see Tables 2 and 4), apparently because predation was great
in all treatments.